The present invention relates to the general field of electro-optical flow measuring devices for characterizing microparticles, in particular biological cells, comprising a measurement chamber in which the flow of the fluid to be characterized circulates and the cells to be characterized are contained. This field is based on analysis methods using electrical and optical measurements to count and differentiate cells contained in a sample to be analysed. The present invention more specifically relates to a multiparametric electro-optical device for cell counting and characterization.
The fluid to be characterized is preferably a blood sample, but it may also be a biological fluid of another type such has cerebrospinal fluid, bone marrow etc. The sample may also contain particles of any type which are to be differentiated and counted.
More specifically, the invention concerns devices comprising at least two light sources, a resistivity measurement device, and several detectors allowing the measurement of an optical parameter, typically extinction measurement and side scatter measurement.
These measurements allow the characterization of biological cells contained in the fluid.
With respect to hematopoietic cells, the person skilled in the art knows that morphological analysis of the cell, obtained by volumetry or diffractometry, including extinction and absorption phenomena, allows discrimination between the main cell lines including erythrocytes or red blood cells, thrombocytes or platelets, and leukocytes or white blood cells. This last population is itself sub-divided into several categories e.g. lymphocytes, monocytes, neutrophils, eosinophils and basophils.
To a certain extent, it is possible to assess the level of maturity of these cells by simultaneously determining their volume and apparent absorption in white light such as described in the patent U.S. Pat. No. 5,138,181 filed by the Applicant. An embodiment of a device developed for near-monochromatic light is described for example in the publication WO 2006/053960.
This assessment of cell maturity is important since it allows early diagnosis to be performed. In general, in the absence of any pathology, the majority of the cells present in the circulating blood are mature cells.
For each of the aforementioned cell types, different maturity levels are known. For example, red blood cells, also known as erythrocytes or red blood corpuscles, are first fabricated in the form of proerythroblasts, then basophilic erythroblasts, and then polychromatophilic erythroblasts. The polychromatophilic erythroblasts develop into acidophilic erythroblasts and then into reticulocytes. It is these reticulocytes that finally differentiate into erythrocytes once they have passed into the circulating blood.
White blood cells or leukocytes are derived from bone marrow in a first form of myeloblasts. These myeloblasts then yield pro-granulocytes that will later change into basophilic, eosinophilic, or neutrophilic granulocytes, first unsegmented but then their nuclei increasingly segment as they mature.
These same myeloblasts are also the origin of the monocyte line which will yield monoblasts, promonocytes, and then the monocytes which will pass into peripheral blood.
The pluripotent stem cell, from which the myeloblast originates, also yields the lymphocyte line via differentiation in the form of a lymphoid stem cell of which part of the line, the T-lymphocyte line, will continue its maturation in the thymus and glands and the other part will remain in the bone marrow to give the B-lymphocyte line. These B-lymphocytes, once activated in the form of plasmocytes, produce antibodies to combat pathogenic antigens.
Blood platelets, or thrombocytes, derive from megakaryoblasts, which originate from the myeloid progenitor from which the myeloblast originated, and once they have arrived at their ultimate maturation stage, i.e. thrombocytogenic megakaryocytes, they produce platelets by disintegration of their cytoplasms. The young platelets, reticulated platelets, have an RNA content that is the remainder of their original cell.
The diagnosis of certain pathologies requires ever finer tuned counting and characterization of hematopoietic cells in circulating blood. In particular, it has become important to be able to bring to light specific populations, such as reticulocytes and erythroblasts, which are immature versions of erythrocytes (red blood cells). Similarly, the bringing to light of immature cells, precursors of leukocytes (called immature lymphocytes, monocytes or granulocytes), is becoming increasingly more important. The classification and counting of activated lymphocytes or of reticulated platelets would also make it possible to obtain a veritable improvement in patient diagnosis.